An installation 2 of the considered type such as illustrated in FIG. 1 comprises a booth 4 delimited by four walls 6, 8, 10, and 12, and a ceiling. A photographic apparatus or camera 14 is placed behind a first wall 6, at the level of a transparent portion of said wall, so that its field of view 16 is directed towards the inside of booth 4 and its focal plane 18 is present inside of said booth.
A second lateral wall 8 of the booth comprises an opening to enable a user 20 to enter into said booth. A seat 22 placed in front of photographic apparatus 14 and close to its focal plane 18 enables the user to sit at a proper distance from the device to have a clear photographic portrait.
Visual marks located at the level of the device help the user place his/her face according to a reference position 24, so that the portrait of his/her face 26 is face-on and centered on the photograph to be taken. The reference position is an area located at the intersection of focal plane 18 and the center of the field of view 14 of the photographic apparatus.
When photographs are taken, a first light source 28 and a second light source 30 placed behind transparent portions of first wall 6 illuminate face 26 of the user. The first and second light sources are respectively placed above and under the photographic apparatus. They are directed and calibrated to illuminate the user's face in reference position 24, in order to decrease contrast areas at the level of his/her face on the photographs.
The first and second light sources illuminate along directions 32 having significant angles of incidence on the user's face, respectively high and low angles. The light sources are directed to complementary illuminate the different reliefs of the user's face and calibrated to illuminate the reference position with the same intensity. More specifically, the shadows formed by the light originating from one of the light sources are illuminated by the light originating from the other light source. Thus, the entire face is illuminated to limit the contrast of the face on the photograph.
However, a poor positioning of the user's face, that is, a positioning slightly offset from reference position 24, may cause an overexposure of certain portions of his/her face with respect to others. According to the morphology and to the position of the face, shadows may then form and no longer be sufficiently illuminated by the other light source. High-contrast areas then appear on the photograph, which is not desirable. For example, as illustrated in FIG. 2A, too high a positioning of the face with respect to the optical axis of the photographic apparatus and a slight inclination of the top of the face towards the first wall favor an overexposure by the first light source of prominent areas of the face, such as forehead 34, nose 36, and chin 38. Such prominent areas form shadows, such as for example chin 38 or a shirt at the level of neck 40, which are illuminated with less intensity since they are located at a greater distance from the second light source with respect to the reference position. The user's photographic portrait then comprises high-contrast areas, capable of masking certain portions of his/her face. The photographic portrait is then incomplete and is likely not to fulfill the requirements for forming a passport or any other official documents. In other words, the photographic portraits may be unusable.
Further, these two light sources at the front have other disadvantages: one can indeed observe an erasing of the relief of the face, which then seems pale, an enhancing of the shine in the presence of stronger sweating of certain portions of the face (particularly on the large planar surfaces of the face such as the forehead).
To partly overcome these disadvantages, it is known to provide another light source, located at the level of wall 12, that is, positioned behind the user. Such a light source is intended to suppress the shadows cast on the background of the booth, and to provide a homogeneous light grey all over the background, by saturation of the photographic apparatus or camera.
To decrease the contrast, a solution may comprise increasing the sensitivity of the sensor or of the film of the photographic apparatus. Unfortunately, the noise of the photograph then increases proportionally, which translates as a decrease in its quality. Further, the sensitivity increase increases the intensity of the most exposed areas, which may then be overexposed. White tinted areas adversely affecting the quality of the photograph may thus appear.
Another solution may also comprise increasing the intensity of the light illuminating the user. Here again, this is not ideal since too high a light intensity causes a discomfort for the user, diminishes the color rendering by overexposing his/her face, and darkens the background. Photographs where the user's face is pale are then obtained.
The Applicant provides an installation for the acquisition of photographic portraits taking high-quality photographs, including when the user's position is approximate in front of the photographic apparatus of said machine.